This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. X-ray crystallography studies show that binding of certain antiestrogen drugs like hydroxytamoxifen induce a conformational change in helix 12 that is substantially different from the conformational change upon binding of estrogen. This difference is presumed to be the structural cause of inhibition. However, the crystal structures of the related estrogen-related receptor gamma shows an identical structure regardless of whether the ligand or the inhibitor is bound. The purpose of this project is to determine if the observed differences in helix 12 in the estrogen receptor is a solution-phase phenomenon, or if it is an artifact of crystallization.